Technically, anything flat can be used as an animation stand, including a basic table. Some are just tables with measurement and placement marks on them. Others are more complicated, with clamps, special fixtures, and special capabilities, such as sliding and rotating. Some have the camera arms and supports mounted on the table, while others keep the camera arms and supports separated. Many that include pegs have grooves for the pegs to slide so they can be repositioned according to the animator's needs.
Depending on the style of animation, the camera (also known as a rostrum camera) may be positioned directly above the stand, or may be positioned to one side of the table with a free range of movement. Cel animation and other 2D animation styles require the camera to be positioned above the stand, centered over the scene and pointed straight down so that the animated frame perfectly fills the camera's field of vision with no tilt. While the camera can often pan back and forth or zoom in and out, allowing animations of panoramic backgrounds or adding an extra layer of motion on top of what's animated on the cels, it's still essentially capturing photos of 2D images for sequencing to video.
In claymation / stop-motion animation, however, the camera needs to be able to film the scene from multiple angles. The scene is set up on the animation stand and captured at more normal angles, much like live action films, before the animator adjusts the claymation models for the next frame and takes another capture. The camera can be adjusted for a full three hundred and sixty degree range of motion, though often this can require use of handheld cameras rather than fixed cameras attached to the stand or their own dolly or tripod.
Professional animation stands can be extremely expensive, with numerous advanced features and attachments. Basic animation stands can be fairly inexpensive, though, ranging in the hundreds of dollars. It's also possible to create your own animation stand, using just a table, stick pins, a camera, a tripod, and markers or tape.
Using a basic table, you can mark off various registration points using a marker or tape to note standard measurements and basic registration marks for proper positioning of your standard size frame (which should be fairly easy if you use 8.5" x 11" letter-size paper or acetate cels). You can then either affix a camera on a tripod positioned over the center of the main working area, pointed straight downward, or you can mount the camera on a stand with a horizontal tripod arm. The horizontal tripod arm can allow more freedom of movement, such as panning, arcing, and zooming. In the absence of pegs, you can use push pins as a substitute - or you can use simple tape to tape your frames into place, though this can start to make a mess over time.
Those with a more DIY bent can even practice a little carpentry and make a homemade animation stand complete with sliding pegs and all the bells and whistles you can possibly install without losing your thumb to a circular saw.